Step Strain-Simulated Relaxation Modulus Curves

3 Step Strain-Simulated Relaxation Modulus Curves 

The step strain-simulated Gs t) curves obtained at A = 0.2 and 0.5 are compared with equilibrium-simulated Gs t) ones in Fig. 17.5 for the two-, five-, ten- and twenty-bead Fraenkel chains. There are clear differences between the equilibrium-simulated curves and the step strain-simulated at A = 0.2 in the cases of two- and five-bead chains, indicating that the fluctuation-dissipation theorem is not fulfilled totally as in the Rouse-chain case. This may be due to A = 0.2 not being in the linear region yet as some small differences can be observed between the Gs t) curves at A = 0.2 and 0.5. In fact, the numerically calculated Gs(0) values as a function of the strain A 

As shown in Fig. 17.5, differences between the equilibrium-simulated and step strain-simulated Gs t) curves occur mainly in the cases of = 2 and 5 and virtually no differences can be observed for A = 10 and 20 even though A = 0.2 and 0.5 are not really in the linear region. In the N = 2 case, while the whole shapes of the Gs(t) curves are very similar, differences can be observed in different regions. In the N = 5 case, the difference becomes obvious in the early part of the slow mode, where an effect related to the coupling between S t) and bx t)by t) — a subject discussed in the 

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